Intensity Behaviour of Exchange Reflexions in LEED from an Antiferromagnetic Crystal

The fundamental equations of the dynamical theory of electron diffraction by an antiferromagnetic crystal are formulated by taking account of the spin dependent part of the exchange interaction between the incoming electron and the magnetic electrons in the crystal. As an application, the effect of intensity enhancement of a weak exchange reflexion with half-order indices in LEED caused by the simultaneous presence of a strong Bragg reflexion with ordinary indices is dealt with; the result generally agrees with previous LEED observation by the present authors on NiO (J. Phys. Soc. Japan 31 (1971) 1408). The values of Fourier components of the scattering factors due to the spin dependent part of the exchange interaction numerically calculated for various electron energies for NiO are found to be in a range of 1/10∼1/20 of ordinary Fourier potentials.